Registers an event handler to this task. Any event filters are first processed, then the
specified onFoo event handlers, and finally any event handlers registered by this method.
As with other events in the scene graph, if an event is consumed, it will not continue
dispatching.

Unregisters a previously registered event filter from this task. One filter might have been
registered for different event types, so the caller needs to specify the particular event
type from which to unregister the filter.

Unregisters a previously registered event handler from this task. One handler might have been
registered for different event types, so the caller needs to specify the particular event type
from which to unregister the handler.